This invention relates to electrical contacts, for example as employed in starting switches used with fractional horsepower electric motors, and, in particular, to a switch which prevents tack welding of the switch contacts. While the invention is described in particular detail with respect to such switches, those skilled in the art will recognize the broader applicability of the invention disclosed hereinafter.
A prior art switch 100 is shown in FIG. 1. Switch 100 may be a switch such as is described in U.S. Pat. No. 4,302,649, which is incorporated herein by reference. The switch includes two terminals T1 and T2 each of which has a contact C1 and C2, respectively. The two contacts are brought together by an arm 101. Often, the switch operation over a period of time causes or attempts to cause the contacts to tack weld together. The terminal T2 has an arm 103 on which contact C2 is mounted. Arm 103 forms a leaf spring and generally has sufficient force to break the weld and separate the contacts. In particular, the switch assembly of FIG. 1 finds application with capacitor start motors. These kinds of motors have relatively low starting currents compared, for example, to a split phase motor. In adopting the switch of FIG. 1 to other motor types, certain problems developed. When motor starting current is increased, such as when the switch is used with a split phase motor, rather than a capacitor start motor, the weld becomes more tenacious. In these instances, the the spring force of the arm 103 is insufficient to break the weld and the contacts are not separated. In the case of a motor with starting windings, which require disconnection during normal run conditions, the starting windings will not be disconnected if the switch is not returned to its normal run position. This causes the starting windings to open, ruining the motor.